In the prior art bis(N-alkylphthalimides) have been prepared by coupling nitro-N-alkylphthalimides. This method results in the preparation of intermediates that are gummy solids that are difficult to handle and present purification problems. See U.S. Pat. No. 3,957,862; U.S. Pat. No. 4,017,511; U.S. Pat. No. 3,956,320 and U.S. Pat. No. 3,972,902.
The prior art has recognized that aryl and heteroaryl polyhalides may be coupled by using an anhydrous nickel catalyst. The polyhalides have been converted into polymers due to the presence of at least two halogen atoms in the starting material. Such a process is described in European patent application 79104205.4. Nothing in that application suggests the coupling of monohalide compounds to form a bisimide.
Polyetherimide polymers are known which all are synthesized from biphenol-di (N-methylphthalimide). See for example U.S. Pat. No. 3,983,093. This compound when converted to the dianhydride may be employed to make polyetherimide polymers. The applicant has discovered a novel process for making certain bis(N-alkylphthalimides) that is easily carried out in conventional equipment. The dianhydride derivatives of these compounds may be utilized in making homopolymers and copolymers using diamine coupling agents.
Thus it is a primary object of this invention to provide a novel method for the preparation of certain bis (N-alkylphthalimides) and dianhydrides derived therefrom.
It is also an object of this invention to provide a novel copolymer that is based on the coupling of a dianhydride of certain bis(N-alkylphthalimide) compounds with a dianhydride derivative of certain bisphenols.